Oogenesis in Lucilia Cuprina (Wied.) (Diptera: Calliphoridae). I. Development of Nurse Cell Nuclei, the Oocyte Nucleus and the Follicle Cells.

Abstract

In investigations in the laboratory in Australia, endomitosis in the ovarian nurse cell nuclei in females of Lucilia cuprina (Wied.) was found to be initiated in stage-1 follicles shortly after eclosion, independently of a protein meal. The largest nurse cell nuclei attained a ploidy of 1024n in stage 3 and 4 follicles, shortly after the onset of vitellogenesis; after this, they could undergo a further eightfold increase in volume. Polytene chromosomes were occasionally observed during endomitosis in 16n and 32n nurse cell nuclei. Throughout stages 1-8, the oocyte nucleus steadily increased from an average diameter of 6-7 mu m to one of about 60 mu m. In early stage 9, the nuclear membrane was lost and what appeared to be a karyosphere with a diameter of about 6 mu m was visible. Later in stage 9, the oocyte nucleus was obscured by yolk, and its development beyond this stage was not traced. Follicle cells increased in number from 80 in early stage-1 follicles to 1300 in stage 2. The information presented was required to ascertain the site of action of aziridinyl chemosterilants on ovarian development [see next abstract] and to aid in current research on the production of chromosomal rearrangements by irradiation.